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<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        //状态变化不可逆
        // pending -- fulfilled
        // pending -- rejected
        var p = new Promise((resolve,reject)=>{
            setTimeout(()=>{
                resolve(10)
            },2000)
        })
        console.log(p);

        var r = new Promise((resolve,reject)=>{
            setTimeout(()=>{
                reject(20)
            },2000)
        })
        console.log(r);
    </script>
</body>
</html>